/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.anna.sent.soft.numberpickerlibrary;

import android.content.Context;
import android.hardware.SensorManager;
import android.os.Build;
import android.util.FloatMath;
import android.view.ViewConfiguration;
import android.view.animation.AnimationUtils;
import android.view.animation.Interpolator;

/**
 * <p>
 * This class encapsulates scrolling. You can use scrollers ({@link Scroller} or
 * {@link OverScroller}) to collect the data you need to produce a scrolling
 * animation&mdash;for example, in response to a fling gesture. Scrollers track
 * scroll offsets for you over time, but they don't automatically apply those
 * positions to your view. It's your responsibility to get and apply new
 * coordinates at a rate that will make the scrolling animation look smooth.
 * </p>
 * 
 * <p>
 * Here is a simple example:
 * </p>
 * 
 * <pre>
 * private Scroller mScroller = new Scroller(context);
 * ...
 * public void zoomIn() {
 *     // Revert any animation currently in progress
 *     mScroller.forceFinished(true);
 *     // Start scrolling by providing a starting point and
 *     // the distance to travel
 *     mScroller.startScroll(0, 0, 100, 0);
 *     // Invalidate to request a redraw
 *     invalidate();
 * }
 * </pre>
 * 
 * <p>
 * To track the changing positions of the x/y coordinates, use
 * {@link #computeScrollOffset}. The method returns a boolean to indicate
 * whether the scroller is finished. If it isn't, it means that a fling or
 * programmatic pan operation is still in progress. You can use this method to
 * find the current offsets of the x and y coordinates, for example:
 * </p>
 * 
 * <pre>
 * if (mScroller.computeScrollOffset()) {
 *     // Get current x and y positions
 *     int currX = mScroller.getCurrX();
 *     int currY = mScroller.getCurrY();
 *    ...
 * }
 * </pre>
 */
public class Scroller {
	private int mMode;

	private int mStartX;
	private int mStartY;
	private int mFinalX;
	private int mFinalY;

	private int mMinX;
	private int mMaxX;
	private int mMinY;
	private int mMaxY;

	private int mCurrX;
	private int mCurrY;
	private long mStartTime;
	private int mDuration;
	private float mDurationReciprocal;
	private float mDeltaX;
	private float mDeltaY;
	private boolean mFinished;
	private Interpolator mInterpolator;
	private boolean mFlywheel;

	private float mVelocity;
	private float mCurrVelocity;
	private int mDistance;

	private float mFlingFriction = ViewConfiguration.getScrollFriction();

	private static final int DEFAULT_DURATION = 250;
	private static final int SCROLL_MODE = 0;
	private static final int FLING_MODE = 1;

	private static float DECELERATION_RATE = (float) (Math.log(0.78) / Math
			.log(0.9));
	private static final float INFLEXION = 0.35f; // Tension lines cross at
													// (INFLEXION, 1)
	private static final float START_TENSION = 0.5f;
	private static final float END_TENSION = 1.0f;
	private static final float P1 = START_TENSION * INFLEXION;
	private static final float P2 = 1.0f - END_TENSION * (1.0f - INFLEXION);

	private static final int NB_SAMPLES = 100;
	private static final float[] SPLINE_POSITION = new float[NB_SAMPLES + 1];
	private static final float[] SPLINE_TIME = new float[NB_SAMPLES + 1];

	private float mDeceleration;
	private final float mPpi;

	// A context-specific coefficient adjusted to physical values.
	private float mPhysicalCoeff;

	static {
		float x_min = 0.0f;
		float y_min = 0.0f;
		for (int i = 0; i < NB_SAMPLES; i++) {
			final float alpha = (float) i / NB_SAMPLES;

			float x_max = 1.0f;
			float x, tx, coef;
			while (true) {
				x = x_min + (x_max - x_min) / 2.0f;
				coef = 3.0f * x * (1.0f - x);
				tx = coef * ((1.0f - x) * P1 + x * P2) + x * x * x;
				if (Math.abs(tx - alpha) < 1E-5)
					break;
				if (tx > alpha)
					x_max = x;
				else
					x_min = x;
			}
			SPLINE_POSITION[i] = coef * ((1.0f - x) * START_TENSION + x) + x
					* x * x;

			float y_max = 1.0f;
			float y, dy;
			while (true) {
				y = y_min + (y_max - y_min) / 2.0f;
				coef = 3.0f * y * (1.0f - y);
				dy = coef * ((1.0f - y) * START_TENSION + y) + y * y * y;
				if (Math.abs(dy - alpha) < 1E-5)
					break;
				if (dy > alpha)
					y_max = y;
				else
					y_min = y;
			}
			SPLINE_TIME[i] = coef * ((1.0f - y) * P1 + y * P2) + y * y * y;
		}
		SPLINE_POSITION[NB_SAMPLES] = SPLINE_TIME[NB_SAMPLES] = 1.0f;

		// This controls the viscous fluid effect (how much of it)
		sViscousFluidScale = 8.0f;
		// must be set to 1.0 (used in viscousFluid())
		sViscousFluidNormalize = 1.0f;
		sViscousFluidNormalize = 1.0f / viscousFluid(1.0f);

	}

	private static float sViscousFluidScale;
	private static float sViscousFluidNormalize;

	/**
	 * Create a Scroller with the default duration and interpolator.
	 */
	public Scroller(Context context) {
		this(context, null);
	}

	/**
	 * Create a Scroller with the specified interpolator. If the interpolator is
	 * null, the default (viscous) interpolator will be used. "Flywheel"
	 * behavior will be in effect for apps targeting Honeycomb or newer.
	 */
	public Scroller(Context context, Interpolator interpolator) {
		this(
				context,
				interpolator,
				context.getApplicationInfo().targetSdkVersion >= Build.VERSION_CODES.HONEYCOMB);
	}

	/**
	 * Create a Scroller with the specified interpolator. If the interpolator is
	 * null, the default (viscous) interpolator will be used. Specify whether or
	 * not to support progressive "flywheel" behavior in flinging.
	 */
	public Scroller(Context context, Interpolator interpolator, boolean flywheel) {
		mFinished = true;
		mInterpolator = interpolator;
		mPpi = context.getResources().getDisplayMetrics().density * 160.0f;
		mDeceleration = computeDeceleration(ViewConfiguration
				.getScrollFriction());
		mFlywheel = flywheel;

		mPhysicalCoeff = computeDeceleration(0.84f); // look and feel tuning
	}

	/**
	 * The amount of friction applied to flings. The default value is
	 * {@link ViewConfiguration#getScrollFriction}.
	 * 
	 * @param friction
	 *            A scalar dimension-less value representing the coefficient of
	 *            friction.
	 */
	public final void setFriction(float friction) {
		mDeceleration = computeDeceleration(friction);
		mFlingFriction = friction;
	}

	private float computeDeceleration(float friction) {
		return SensorManager.GRAVITY_EARTH // g (m/s^2)
				* 39.37f // inch/meter
				* mPpi // pixels per inch
				* friction;
	}

	/**
	 * 
	 * Returns whether the scroller has finished scrolling.
	 * 
	 * @return True if the scroller has finished scrolling, false otherwise.
	 */
	public final boolean isFinished() {
		return mFinished;
	}

	/**
	 * Force the finished field to a particular value.
	 * 
	 * @param finished
	 *            The new finished value.
	 */
	public final void forceFinished(boolean finished) {
		mFinished = finished;
	}

	/**
	 * Returns how long the scroll event will take, in milliseconds.
	 * 
	 * @return The duration of the scroll in milliseconds.
	 */
	public final int getDuration() {
		return mDuration;
	}

	/**
	 * Returns the current X offset in the scroll.
	 * 
	 * @return The new X offset as an absolute distance from the origin.
	 */
	public final int getCurrX() {
		return mCurrX;
	}

	/**
	 * Returns the current Y offset in the scroll.
	 * 
	 * @return The new Y offset as an absolute distance from the origin.
	 */
	public final int getCurrY() {
		return mCurrY;
	}

	/**
	 * Returns the current velocity.
	 * 
	 * @return The original velocity less the deceleration. Result may be
	 *         negative.
	 */
	public float getCurrVelocity() {
		return mMode == FLING_MODE ? mCurrVelocity : mVelocity - mDeceleration
				* timePassed() / 2000.0f;
	}

	/**
	 * Returns the start X offset in the scroll.
	 * 
	 * @return The start X offset as an absolute distance from the origin.
	 */
	public final int getStartX() {
		return mStartX;
	}

	/**
	 * Returns the start Y offset in the scroll.
	 * 
	 * @return The start Y offset as an absolute distance from the origin.
	 */
	public final int getStartY() {
		return mStartY;
	}

	/**
	 * Returns where the scroll will end. Valid only for "fling" scrolls.
	 * 
	 * @return The final X offset as an absolute distance from the origin.
	 */
	public final int getFinalX() {
		return mFinalX;
	}

	/**
	 * Returns where the scroll will end. Valid only for "fling" scrolls.
	 * 
	 * @return The final Y offset as an absolute distance from the origin.
	 */
	public final int getFinalY() {
		return mFinalY;
	}

	/**
	 * Call this when you want to know the new location. If it returns true, the
	 * animation is not yet finished.
	 */
	public boolean computeScrollOffset() {
		if (mFinished) {
			return false;
		}

		int timePassed = (int) (AnimationUtils.currentAnimationTimeMillis() - mStartTime);

		if (timePassed < mDuration) {
			switch (mMode) {
			case SCROLL_MODE:
				float x = timePassed * mDurationReciprocal;

				if (mInterpolator == null)
					x = viscousFluid(x);
				else
					x = mInterpolator.getInterpolation(x);

				mCurrX = mStartX + Math.round(x * mDeltaX);
				mCurrY = mStartY + Math.round(x * mDeltaY);
				break;
			case FLING_MODE:
				final float t = (float) timePassed / mDuration;
				final int index = (int) (NB_SAMPLES * t);
				float distanceCoef = 1.f;
				float velocityCoef = 0.f;
				if (index < NB_SAMPLES) {
					final float t_inf = (float) index / NB_SAMPLES;
					final float t_sup = (float) (index + 1) / NB_SAMPLES;
					final float d_inf = SPLINE_POSITION[index];
					final float d_sup = SPLINE_POSITION[index + 1];
					velocityCoef = (d_sup - d_inf) / (t_sup - t_inf);
					distanceCoef = d_inf + (t - t_inf) * velocityCoef;
				}

				mCurrVelocity = velocityCoef * mDistance / mDuration * 1000.0f;

				mCurrX = mStartX
						+ Math.round(distanceCoef * (mFinalX - mStartX));
				// Pin to mMinX <= mCurrX <= mMaxX
				mCurrX = Math.min(mCurrX, mMaxX);
				mCurrX = Math.max(mCurrX, mMinX);

				mCurrY = mStartY
						+ Math.round(distanceCoef * (mFinalY - mStartY));
				// Pin to mMinY <= mCurrY <= mMaxY
				mCurrY = Math.min(mCurrY, mMaxY);
				mCurrY = Math.max(mCurrY, mMinY);

				if (mCurrX == mFinalX && mCurrY == mFinalY) {
					mFinished = true;
				}

				break;
			}
		} else {
			mCurrX = mFinalX;
			mCurrY = mFinalY;
			mFinished = true;
		}
		return true;
	}

	/**
	 * Start scrolling by providing a starting point and the distance to travel.
	 * The scroll will use the default value of 250 milliseconds for the
	 * duration.
	 * 
	 * @param startX
	 *            Starting horizontal scroll offset in pixels. Positive numbers
	 *            will scroll the content to the left.
	 * @param startY
	 *            Starting vertical scroll offset in pixels. Positive numbers
	 *            will scroll the content up.
	 * @param dx
	 *            Horizontal distance to travel. Positive numbers will scroll
	 *            the content to the left.
	 * @param dy
	 *            Vertical distance to travel. Positive numbers will scroll the
	 *            content up.
	 */
	public void startScroll(int startX, int startY, int dx, int dy) {
		startScroll(startX, startY, dx, dy, DEFAULT_DURATION);
	}

	/**
	 * Start scrolling by providing a starting point, the distance to travel,
	 * and the duration of the scroll.
	 * 
	 * @param startX
	 *            Starting horizontal scroll offset in pixels. Positive numbers
	 *            will scroll the content to the left.
	 * @param startY
	 *            Starting vertical scroll offset in pixels. Positive numbers
	 *            will scroll the content up.
	 * @param dx
	 *            Horizontal distance to travel. Positive numbers will scroll
	 *            the content to the left.
	 * @param dy
	 *            Vertical distance to travel. Positive numbers will scroll the
	 *            content up.
	 * @param duration
	 *            Duration of the scroll in milliseconds.
	 */
	public void startScroll(int startX, int startY, int dx, int dy, int duration) {
		mMode = SCROLL_MODE;
		mFinished = false;
		mDuration = duration;
		mStartTime = AnimationUtils.currentAnimationTimeMillis();
		mStartX = startX;
		mStartY = startY;
		mFinalX = startX + dx;
		mFinalY = startY + dy;
		mDeltaX = dx;
		mDeltaY = dy;
		mDurationReciprocal = 1.0f / (float) mDuration;
	}

	/**
	 * Start scrolling based on a fling gesture. The distance travelled will
	 * depend on the initial velocity of the fling.
	 * 
	 * @param startX
	 *            Starting point of the scroll (X)
	 * @param startY
	 *            Starting point of the scroll (Y)
	 * @param velocityX
	 *            Initial velocity of the fling (X) measured in pixels per
	 *            second.
	 * @param velocityY
	 *            Initial velocity of the fling (Y) measured in pixels per
	 *            second
	 * @param minX
	 *            Minimum X value. The scroller will not scroll past this point.
	 * @param maxX
	 *            Maximum X value. The scroller will not scroll past this point.
	 * @param minY
	 *            Minimum Y value. The scroller will not scroll past this point.
	 * @param maxY
	 *            Maximum Y value. The scroller will not scroll past this point.
	 */
	public void fling(int startX, int startY, int velocityX, int velocityY,
			int minX, int maxX, int minY, int maxY) {
		// Continue a scroll or fling in progress
		if (mFlywheel && !mFinished) {
			float oldVel = getCurrVelocity();

			float dx = (float) (mFinalX - mStartX);
			float dy = (float) (mFinalY - mStartY);
			float hyp = FloatMath.sqrt(dx * dx + dy * dy);

			float ndx = dx / hyp;
			float ndy = dy / hyp;

			float oldVelocityX = ndx * oldVel;
			float oldVelocityY = ndy * oldVel;
			if (Math.signum(velocityX) == Math.signum(oldVelocityX)
					&& Math.signum(velocityY) == Math.signum(oldVelocityY)) {
				velocityX += oldVelocityX;
				velocityY += oldVelocityY;
			}
		}

		mMode = FLING_MODE;
		mFinished = false;

		float velocity = FloatMath.sqrt(velocityX * velocityX + velocityY
				* velocityY);

		mVelocity = velocity;
		mDuration = getSplineFlingDuration(velocity);
		mStartTime = AnimationUtils.currentAnimationTimeMillis();
		mStartX = startX;
		mStartY = startY;

		float coeffX = velocity == 0 ? 1.0f : velocityX / velocity;
		float coeffY = velocity == 0 ? 1.0f : velocityY / velocity;

		double totalDistance = getSplineFlingDistance(velocity);
		mDistance = (int) (totalDistance * Math.signum(velocity));

		mMinX = minX;
		mMaxX = maxX;
		mMinY = minY;
		mMaxY = maxY;

		mFinalX = startX + (int) Math.round(totalDistance * coeffX);
		// Pin to mMinX <= mFinalX <= mMaxX
		mFinalX = Math.min(mFinalX, mMaxX);
		mFinalX = Math.max(mFinalX, mMinX);

		mFinalY = startY + (int) Math.round(totalDistance * coeffY);
		// Pin to mMinY <= mFinalY <= mMaxY
		mFinalY = Math.min(mFinalY, mMaxY);
		mFinalY = Math.max(mFinalY, mMinY);
	}

	private double getSplineDeceleration(float velocity) {
		return Math.log(INFLEXION * Math.abs(velocity)
				/ (mFlingFriction * mPhysicalCoeff));
	}

	private int getSplineFlingDuration(float velocity) {
		final double l = getSplineDeceleration(velocity);
		final double decelMinusOne = DECELERATION_RATE - 1.0;
		return (int) (1000.0 * Math.exp(l / decelMinusOne));
	}

	private double getSplineFlingDistance(float velocity) {
		final double l = getSplineDeceleration(velocity);
		final double decelMinusOne = DECELERATION_RATE - 1.0;
		return mFlingFriction * mPhysicalCoeff
				* Math.exp(DECELERATION_RATE / decelMinusOne * l);
	}

	static float viscousFluid(float x) {
		x *= sViscousFluidScale;
		if (x < 1.0f) {
			x -= (1.0f - (float) Math.exp(-x));
		} else {
			float start = 0.36787944117f; // 1/e == exp(-1)
			x = 1.0f - (float) Math.exp(1.0f - x);
			x = start + x * (1.0f - start);
		}
		x *= sViscousFluidNormalize;
		return x;
	}

	/**
	 * Stops the animation. Contrary to {@link #forceFinished(boolean)},
	 * aborting the animating cause the scroller to move to the final x and y
	 * position
	 * 
	 * @see #forceFinished(boolean)
	 */
	public void abortAnimation() {
		mCurrX = mFinalX;
		mCurrY = mFinalY;
		mFinished = true;
	}

	/**
	 * Extend the scroll animation. This allows a running animation to scroll
	 * further and longer, when used with {@link #setFinalX(int)} or
	 * {@link #setFinalY(int)}.
	 * 
	 * @param extend
	 *            Additional time to scroll in milliseconds.
	 * @see #setFinalX(int)
	 * @see #setFinalY(int)
	 */
	public void extendDuration(int extend) {
		int passed = timePassed();
		mDuration = passed + extend;
		mDurationReciprocal = 1.0f / mDuration;
		mFinished = false;
	}

	/**
	 * Returns the time elapsed since the beginning of the scrolling.
	 * 
	 * @return The elapsed time in milliseconds.
	 */
	public int timePassed() {
		return (int) (AnimationUtils.currentAnimationTimeMillis() - mStartTime);
	}

	/**
	 * Sets the final position (X) for this scroller.
	 * 
	 * @param newX
	 *            The new X offset as an absolute distance from the origin.
	 * @see #extendDuration(int)
	 * @see #setFinalY(int)
	 */
	public void setFinalX(int newX) {
		mFinalX = newX;
		mDeltaX = mFinalX - mStartX;
		mFinished = false;
	}

	/**
	 * Sets the final position (Y) for this scroller.
	 * 
	 * @param newY
	 *            The new Y offset as an absolute distance from the origin.
	 * @see #extendDuration(int)
	 * @see #setFinalX(int)
	 */
	public void setFinalY(int newY) {
		mFinalY = newY;
		mDeltaY = mFinalY - mStartY;
		mFinished = false;
	}

	/**
	 * @hide
	 */
	public boolean isScrollingInDirection(float xvel, float yvel) {
		return !mFinished
				&& Math.signum(xvel) == Math.signum(mFinalX - mStartX)
				&& Math.signum(yvel) == Math.signum(mFinalY - mStartY);
	}
}
